Drip irrigation involves slowly metering various agricultural fluids, such as water, adjacent each plant which is to be grown. Normally, the metering of these fluids is carried out over a relatively long time period. Drip irrigation conserves water, minimizes weed growth and enables various agricultural liquids such as fertilizers to be fed through the irrigation system.
It is very important that the flow rate for drip irrigation systems be adjustable. For example, where drip irrigation is used in an orchard, more water must be applied as the trees grow. A conventional technique is to increase the number of emitter valves at the base of each of the trees as the trees grow. However, this unnecessarily duplicates the emitter valves and require significant labor cost to install the additional valves.
Valves which can be used to adjust the flow rate are not novel per se, as evidenced, for example, by Prosser U.S. Pat. No. 3,322,145 and Toeppen U.S. Pat. No. 3,341,168. However, neither of these patented valves is a drip irrigation valve and both are relatively complex.
With drip irrigation, it is important that the water be accurately metered. Unfortunately, water sources often provide water at fluctuating pressures, which, if ignored, would significantly effect flow rate onto the plant. In addition, when fields and irrigation lines are on a slope, more pressure is available at the lower elevations than at the higher elevations.
To provide pressure control, master pressure regulators can be used, but these increase the cost of the irrigation system. Pressure compensating emitter valves, such as the valves shown in Rondas U.S. Pat. No. 3,693,888 can be used. However, the patented valve has minute passages which are subject to clogging. In addition, the patented construction has no means for manually adjusting the flow rate.